The impossibilities of Herodotus’ story are so manifest that it is hardly necessary to point them out. How could the commissariat of a large force have been provided for on a march of that length through a hostile country where the natives, according to the historian’s own account, destroyed all local food supplies in advance of the army? How could the army and the transport required for it have been carried across such rivers as would have to be passed ere the Volga was reached,—the Sereth, the Pruth, the Dniester, Dnieper, Boug, and Don, not to mention numerous minor unfordable streams? If this long march was undertaken, why did not Darius employ the fleet for commissariat purposes, as was the custom in Persian campaigns of this age, where the fleet could possibly be employed? If the fleet did remain at the Ister, which seems to be one of the few absolutely reliable statements in the story, the fact itself is strong presumptive evidence that Darius did not intend to go far beyond that river. Ktesias says he only proceeded fifteen days’ march. Strabo implies that he never reached the Dniester. Inasmuch as the reliability of Herodotus as an historian is in question, it is important to make an attempt to surmise, in so far as possible, what was the source or sources of this extraordinary tale which he has preserved. It must be remembered, in the first place, that at the time at which he wrote, anything of the nature of reliable information with regard to events before the war of 480 must have been very difficult to obtain. The palpable gaps in the story of the Ionian Revolt, the confusion in the account of the relations between Athens and Ægina, the meagreness of the story of Marathon, are striking proofs that such was the case; and if he experienced such manifest difficulty in arriving at a detailed knowledge of the great events of the beginning of the fifth century, in which Greeks played a foremost part, how much greater difficulty must he have experienced in gaining information as to the events of the later years of the sixth century, in which the part played by the Greeks was but secondary? It seems probable that his sources of information in the present instance were two in number:— (1) A tale current in the Athens of his own day, which had come thither by way of the principality of Miltiades in the Thracian Chersonese. (2) Reports collected by the historian himself, either in the course of a journey to the Greek colonies on the north coast of the Euxine, or from persons who were natives of those parts, or had visited them. To the first of these must be attributed the account which he gives of the events on the Danube, and especially the celebrated tale of the proposal of Miltiades to break down the bridge and leave Darius to his fate.